This invention relates to gas phase dehydrohalogenation processes using pretreated catalysts.
Vinylidene chloride and related unsaturated, halogenated organic compounds are important monomers leading to many polymeric materials. In U.S. Pat. No. 2,803,677, a method is disclosed wherein 1,1,1-trichloroethane is dehydrochlorinated in the gas phase over activated alumina. The reference reports that at a temperature of 250.degree. C., the method produces a 95.8% yield of vinylidene chloride. However, the process produces poor yields at lower temperatures and the lifetime of the catalyst is relatively short. Lower temperatures are desirable because production costs are reduced. What is needed is a process which increases the conversion rate of halogenated hydrocarbons in gas phase reactions to unsaturated compounds over alumina, preferably at low reaction temperatures. Likewise, a process which would increase the lifetime of the alumina catalyst would be desirable.
Additionally, the prior art generally lacks efficient gas phase catalytic dehydrohalogenation processes using catalysts other than alumina. The public would benefit from such processes due to the increased knowledge in this technology and due to the advantages associated with gas phase processes such as low production costs and reduced waste relative to liquid phase processes.